1. Field of the Invention
This invention is directed to bone implants and in particular to prostheses for total joint replacement.
2. Discussion of Related Art
Total joint replacement is now becoming a commonplace method of treating disorders, such as acute arthritis, where the diseased joint is removed surgically and replaced with an artificial joint. As such operations have become more common, problems arising from long-term wear of such joints have become apparent. In a number of instances, it is found that bone resorption occurs in the region of the implant which leads to the loosening of the implant in the bone canal, and the breakdown of any cement mantle between the implant and the bone canal.
Various suggestions have been made as to the cause of such degeneration. It is believed that a primary reason for this loosening is the ingress of wear particles, generated by prolonged movement of the articulating surfaces of the joint and that such particles migrate from the area of articulation into the junction between the implant and the bone. It is believed that wear particles generated in this way at the articulating surfaces migrate along the cement/metal interface (or between the bone and the implant), and cause endosteal erosion. Progressive erosion ultimately causes breakdown of the cement mantle or sufficient loosening of a cement-less stem such that it can become displaced from the bone canal or socket.